“it‟s not over till it‟s over” - flight test...
TRANSCRIPT
© Copyright 2009 Lockheed Martin Corporation
F-16 E/F Automatic Terrain Following Development:
“It‟s Not Over Till It‟s Over”
Billie Flynn
Experimental Test Pilot
Lockheed Martin Aeronautics Company
© Copyright 2009 Lockheed Martin Corporation 2
© Copyright 2009 Lockheed Martin Corporation 3
Overview
Super Viper Description
TF Overview
RTF Overwater Incident
DBTF Desert Butte Incident
Summary
Lessons Re-Learned
???
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Video Conferencing
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F-16 E/F – A New Fighter
AIRFRAME/ SYSTEMS
• 50,000 lb Max TOGW
• 44,500 lb Max Landing Wt
• Dual ECS
• NVIS Exterior / Strip Lighting
• Equipment Dorsal
• Conformal Fuel Tanks
PROPULSION• F110-GE-132
• Autothrottle
ADVANCED SENSORS
• Agile Beam Radar
• Integrated FLIR & Targeting System
• Radar Auto Terrain Following
• Internal Electronic Warfare Suite
• Countermeasures Dispenser System
NEW AVIONICS• Mission Computer
• Color Display Processor
• Fiber Optic Architecture
• Data Link, Com & Nav System
• IFF Interrogator
FLIGHT CONTROL SYSTEMS
• Upgraded Digital Flight Controls
• New Air Data System
• Next Generation Autopilot
• Auto Ground Collision Avoidance System
• Pilot Activated Recovery System
• Auto Deep Stall Recovery
ADVANCED COCKPIT•Revamped Pilot Interface
•Color Glass Cockpit
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Full Color, All Digital Cockpit
Three 5 x 7 inch Primary
Multi-Function Color Displays
Windowing Capability, Nine Displays
Within Three
Fused Sensor Data Presented Pilot
Intuitive HOTAS Controls Optimized
Through Combat Operations
Fully NVIS Compatible
Combat-Optimized Man Machine Interface
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PVI – Sometimes Nothing Helps
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Terrain Following (TF) Capabilities
Radar Terrain Following (RTF) – Active mode
Stand-alone or interleaved radar modes
Database Terrain Following (DBTF) – Passive mode
Manual or automatic capability with autopilot modes
Fully coupled operation
System Wide Integrity Monitoring for fault detection
RTF / DBTF - Integrated operation
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Radar Terrain Following
Radar senses terrain and generates climb / dive commands at selected
Set Clearance Plane (SCP)
Flight control system (FLCS) follows commands from radar computer
Control stick coupling of displayed commands in Manual RTF
Direct coupling in Automatic RTF
Radar Altimeter
Checks operation as back-up to radar
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RTF System Block Diagram
MULTI-FUNCTION
DISPLAY
- Terrain Video
AGILE BEAM RADAR
- Terrain Sensing
- Command Generation
DIGITAL FLIGHT
CONTROL SYSTEM
- Command Execution
RADAR
ALTIMETER
-Altitude Above
Ground Level
EMBEDDED
GPS/INS
-Aircraft
State Data
HEAD UP DISPLAY
- Command
Cues
AIRFRAME
SIDE STICK
CONTROLLERPILOT
Aircraft Response
Climb/Dive Command
Auto
Aircraft
Response
Manual Surface
Control
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„E-Squared‟ and Terrain Profile Display
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Data Base Terrain Following
Digital Terrain Elevation Database (DTED)
Scanned to generate 2D Worst Case Profile (WCP) of Terrain
DBTF algorithm scans WCP
Generates climb / dive commands at selected Threshold Crossing Height (TCH)
FLCS follows commands from digital terrain system (DTS) flight software
Control stick coupling of displayed commands in Manual TF
Direct coupling in Automatic TF
Radar Altimeter
Checks operation as back-up to DTS
WCP
TCH
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DBTF Functional Block Diagram
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Who Needs Pilots Anyway???
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RTF Test Development
Robust full envelope expansion
Excellent results
All terrain types
Flat, moderate, mountainous
Low reflective (water / sand)
Adverse weather
Full speed / aircraft weight range
Interleaved radar modes
Simultaneous RTF / SAR map /
Air-to-Air tracks
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RTF Over Water Event
Speed and altitude verification over water
Near end of test program
Gulf of Mexico
Perfect day
Calm water / no wind
Test Point
Auto RTF
600 KCAS / 100 ft AGL / non-turning
Event
Full Command -1 g pushover at 100 ft AGL
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RTF Over Water
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Analysis - Automatic Ground Recovery
0
50
100
150
200
250
0 1 2 3 4 5 6 7 8 9 10 11 12
Time (sec)
AG
L A
ltit
ud
e (
ft)
Radar Altitude
-1
0
1
2
3
4
0 1 2 3 4 5 6 7 8 9 10 11 12
Time (sec)
Accele
rati
on
(g
)
RTF Climb/Dive Command Aircraft Load Factor Vertical Clearance Warning
Minimum of 40 ft AGL
Full pushover command at t = 5 sec
4g flyup
VCW at 84 ftRate limited at -0.6g/sec
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Causes and Solution
Logic anomaly in Radar software only evident under very limited conditions
Few „real‟ radar measurements
Smooth water
Low grazing angle
Specific sequence required
Last complete scan with no radar measurements
Current scan (in progress) with very few measurements at short range
Resultant RTF terrain profile contained erroneous height data
Solution
Ignore any „no measurement‟ data from previous scan
Use near-range radar measurements from current scan to create RTF
terrain profile
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DBTF Test Development
Robust full envelope expansion
Excellent results
All terrain types
Flat, moderate, mountainous
Full speed / aircraft weight range
Good performance against
vertical obstacles
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DBTF Twin Butte Testing
Rough and Moderate testing
completed down to 200 ft AGL
Flat terrain tested down to 100 ft AGL
Test Point
480 KCAS / 200 ft AGL / Auto
Versus single vertical obstacle
Event
Fly-up over Butte when 75% of
TCH incursion
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DBTF Twin Butte Testing
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Legacy Level 1 DTED
Google Earth:
View from aircraft: Legacy Level 1 DTED (rendered by Mission Planning System):
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DTED Levels and Sources
DTED Level Post Spacing Ground Distance
1 3 arc-sec ~300’ (100m)
2 1 arc-sec ~100’ (30m)
Source Remarks
Legacy
(Photogrammetric /
Topographic)Coverage:
Level 1: ~70% of earth’s landmass
Level 2: ~ 10% of earth’s landmass
Issues: Non-homogenous, significant artifacts, “bare
earth”
SRTM
(Shuttle Radar
Topography Mission –
STS-99, Feb 2000)
Coverage: 60 N to 56 S
Issues:
Not “bare earth” (some foliage and obstacles
averaged in)
Voids where low reflectivity (sand, flat, water,
extremely steep)
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Shuttle Radar Topography Mission
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Summary
Robust Terrain Following development
All flight / terrain conditions
Mature „build-down‟ and envelope expansion procedures
Rigorous test process
Many other contributors to a test
Perfectly calm water exposed faulty logic path
Terrain data errors masked TF performance
2 Incidents
Saved by good luck or good test planning???
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Lessons Re-Learned
Never just testing a single discipline
Spec Compliance is not necessarily
Developmental Testing
Development is a Discovery Process
Diligence required until the end
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Questions ???